Modular miniature unmanned aircraft with vectored thrust control

ABSTRACT

An aircraft for unmanned aviation is described. The aircraft includes an airframe, a pair of fins attached to a rear portion of the airframe, a pair of dihedral braces attached to a bottom portion of the airframe, a first thrust vectoring module and a second thrust vectoring module, and an electronics module. The electronics module provides commands to the two thrust vectoring modules. The two thrust vectoring modules are configured to provide lateral and longitudinal control to the aircraft by directly controlling a thrust vector for each of the pitch, the roll, and the yaw of the aircraft. The use of directly articulated electrical motors as thrust vectoring modules enables the aircraft to execute tight-radius turns over a wide range of airspeeds.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention provides a miniature unmanned aircraft. Moreparticularly, the present invention provides an aircraft that usesthrust vectoring modules to enable the aircraft to execute tight-radiusturns at high angular rates over a wide range of speeds.

2. Related Art

The use of unmanned aerial vehicles (UAVs) has become important inrecent years for a wide variety of applications, including militaryuses. In some applications, a UAV may be required to have a capabilityfor maneuvering quickly or in tight spaces. Further, the UAV may berequired to have this capability over a wide range of speeds.

Conventional fixed wing small UAVs generally lack the maneuveringcapability and speed range that would be necessary for operating in anurban canyon. Generally, this is due to a reliance upon airflow overcontrol surfaces derived from the forward airspeed of the vehicle.Vertical takeoff-and-landing (VTOL) aircraft have been used to addressthis maneuvering challenge at low speeds. For example, in U.S. Pat. No.6,719,244, a VTOL aircraft uses lateral tilting of the propellers toinduce unbalanced torque-induced and gyroscopic moments which act on theaircraft about an axis essentially perpendicular to the tilt axis. U.S.Patent Application Publication No. US 2006/0192047 discloses a hoveringair vehicle that uses two ducted fans attached to a common drivehousing. The vanes below each fan body can be tilted differentially orin unison to generate control forces. In one embodiment, fixed wings areattached to the ducts for forward flight capability.

However, in both of these instances, control forces are generatedthrough secondary effects, either gyroscopic or aerodynamic. Thesecontrol forces increase system complexity and limit achievablemaneuverability. Therefore, the present inventors have recognized theneed to develop an aircraft that has such a capability.

SUMMARY OF THE INVENTION

In one aspect, the invention provides an aircraft for unmanned aviation.The aircraft comprises: an airframe; a pair of fins attached to a rearportion of the airframe; a pair of dihedral braces attached to a bottomportion of the airframe; at least a first thrust vectoring module and asecond thrust vectoring module, the at least two thrust vectoringmodules being configured to provide lateral and longitudinal control tothe aircraft by directly controlling a thrust vector; and an electronicsmodule configured to provide commands to the at least two thrustvectoring modules. The at least two thrust vectoring modules may befurther configured to independently control a pitch, a roll, and a yawof the aircraft.

Each of the at least two thrust vectoring modules may comprise adirectly articulated electrical motor. The airframe may be disposableand foldable into a compact, stowable configuration. The aircraft may beconfigured for executing tight-radius turns, including a turn having aradius of less than or equal to one wing span, at high angular rates ofup to one rotation per second, over a wide range of airspeeds, includinga range from zero to a maximum speed of the aircraft, and possiblyincluding a post-stall condition. The airframe may comprise amission-specific airframe, possibly based on an atmospheric condition ora weather condition.

In another aspect, the present invention provides a control system forcontrolling a flight path of an unmanned aerial vehicle. The controlsystem comprises: at least a first thrust vectoring module and a secondthrust vectoring module, and an electronics module. The electronicsmodule is configured to provide commands to the at least two thrustvectoring modules based on instructions received from a user of thecontrol system. The at least two thrust vectoring modules are configuredto provide lateral and longitudinal control to the vehicle by directlycontrolling a thrust vector. The at least two thrust vectoring modulesmay be further configured to independently control a pitch, a roll, anda yaw of the vehicle.

Each of the at least two thrust vectoring modules may comprise adirectly articulated electrical motor. The control system may beconfigured for enabling the vehicle to execute tight-radius turns,including a turn having a radius of less than or equal to one wing span,at high angular rates of up to one rotation per second over a wide rangeof airspeeds, including a range from zero to a maximum airspeed of thevehicle, and possibly including a post-stall condition.

In yet another aspect of the invention, a method for controlling aflight path of an unmanned aerial vehicle is provided. The methodcomprises the steps of: transmitting a control signal to an electronicsmodule, the control signal including instructions for controlling aspeed and a direction of the vehicle; causing the electronics module toprovide a command to each of at least a first thrust vectoring moduleand a second thrust vectoring module; and causing each of the at leastfirst thrust vectoring module and second thrust vectoring module toprovide thrust such that the vehicle is laterally and longitudinallycontrolled. The step of causing each of the at least first and secondthrust vectoring modules to provide thrust may further include causingeach of the at least first and second thrust vectoring modules toindependently control a pitch, a roll, and a yaw of the vehicle.

Each of the at least two thrust vectoring modules may comprise adirectly articulated electrical motor. The step of causing each of theat least first thrust vectoring module and second thrust vectoringmodule to provide thrust such that the vehicle is laterally andlongitudinally controlled may further comprise the step of enabling thevehicle to execute tight-radius turns, including a turn having a radiusof less than or equal to one wing span, at high angular rates of up toone rotation per second over a wide range of airspeeds, including arange of zero to a maximum airspeed of the vehicle, and possiblyincluding a post-stall condition.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features and advantages of the present invention will best beunderstood by reference to the detailed description of the preferredembodiments that follows, when read in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates a modular miniature unmanned aircraft with vectoredthrust control according to a preferred embodiment of the presentinvention in a deployed configuration.

FIG. 2 illustrates a modular miniature unmanned aircraft with vectoredthrust control according to a preferred embodiment of the presentinvention in a stowed configuration.

FIG. 3 illustrates eight major components of a disassembled modularminiature unmanned aircraft with vectored thrust control according to apreferred embodiment of the present invention.

FIG. 4 illustrates an electronics module and two thrust vectoringmodules that serve as components for a modular miniature unmannedaircraft with vectored thrust control according to a preferredembodiment of the present invention.

FIGS. 5 a and 5 b illustrate a thrust vectoring module for use as acomponent for a modular miniature unmanned aircraft with vectored thrustcontrol according to preferred embodiment of the present invention.

FIGS. 6 a, 6 b, 6 c, and 6 d illustrate four directional motions basedon action by the thrust vectoring modules of a modular miniatureunmanned aircraft with vectored thrust control according to a preferredembodiment of the present invention.

FIGS. 7 a, 7 b, 7 c, and 7 d illustrate a folding process for compactlypacking a modular miniature unmanned aircraft with vectored thrustcontrol according to a preferred embodiment of the present invention.

FIGS. 8 a, 8 b, 8 c, and 8 d illustrate a dihedral brace for use as alanding skid and locking element on a modular miniature unmannedaircraft with vectored thrust control according to a preferredembodiment of the present invention.

FIG. 9 illustrates a flow chart for a method of controlling a flightpath of a modular miniature unmanned aircraft with vectored thrustcontrol according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The inventors of the present invention have developed a modularminiature unmanned aircraft with vectored thrust control tosynergistically mesh sensor and aircraft capabilities into a systemcapable of navigating through highly cluttered urban environments.Whereas traditional force production techniques rely on airflow overcontrol surfaces, the modular miniature unmanned aircraft with vectoredthrust control employs articulated motors to directly change the thrustvector, including directly changing both the magnitude and the directionof the thrust vector. This allows the modular miniature unmannedaircraft to execute tight-radius high-angular-rate turns, over a widespeed range and in the post stall regime. In addition, the modularminiature unmanned aircraft features a low aspect ratio planform, whichpermits rapid deceleration/perch maneuvers, and permits benigncontrolled flight at large angles of attack. This feature provides theadditional advantages of reduced system complexity and increaseddurability. Further, all of the moving parts of the modular miniatureunmanned aircraft are preferably co-located in ruggedized pods, makingthe actual airframe a low-cost disposable element of the modularminiature unmanned aircraft system.

In a preferred embodiment, the modular miniature unmanned aircraft withvectored thrust control can execute a turn having a radius of less thanor equal to one wing span. In one embodiment, the modular miniatureunmanned aircraft can have an airspeed of zero with its nose pointingvertically, thereby operating in a hover mode, and then rotate about avertical axis. In addition, when operating in the hover mode, themodular miniature unmanned aircraft can perform a pirouette maneuver ata rate of more than one rotation per second. The maximum angular rate ofthe modular miniature unmanned aircraft is generally a function of theforward airspeed, with the only limitation being equivalent to thephysical limits associated with centrifugal forces at the given forwardairspeed. All turning and rotating maneuvers of the modular miniatureunmanned aircraft can be executed at any forward airspeed between zeroand the maximum forward airspeed of the modular miniature unmannedaircraft itself.

The modular miniature unmanned aircraft configuration has developed intoa scalable series of vehicles, ranging from 100 inches to 6 inches inlength. In one preferred embodiment, the modular miniature unmannedaircraft with vectored thrust control has a full length of 24 inches. Ina preferred embodiment, the 24″ modular miniature unmanned aircraftvehicle has been equipped with a Paparazzi autopilot and has been usedfor flight tests in support of the Micro Air Vehicle Small BusinessInnovative Research grant.

Referring to FIG. 1, an exemplary modular miniature unmanned aircraft100 with vectored thrust control according to a preferred embodiment ofthe present invention is shown in a fully deployed configuration.Referring to FIG. 2, the exemplary modular miniature unmanned aircraft100 is shown in a stowed configuration 700. According to a preferredembodiment of the present invention, the modular miniature unmannedaircraft provides a small modular unmanned vehicle with directlyarticulated electric motors for providing lateral and longitudinalcontrol. The modular miniature unmanned aircraft includes a combinedmotor/actuator vector unit, which typically includes two thrustvectoring (T/V) modules. The T/V modules are deflected in unison forpitch control, and differentially for yaw control. Low mass propellersmitigate unwanted force coupling with motor deflection. The propellers114 can operate in a counter-rotational mode to cancel gyroscopiceffects and improve cruise efficiency due to a reduction in induced dragresulting by spinning in a direction such that the propeller wakeopposes the spin direction of the normal tip vortex.

To provide vertical takeoff-and-landing (VTOL) capability, a tri-motoror quad motor configuration may be used. In a preferred embodiment ofthe invention, the modular miniature unmanned aircraft 100 features amodular vehicle architecture, which facilitates a disposable, foldingairframe 102 and the use of mission-specific airframes. For example, asmaller planform could be used in gusty environments.

Referring to FIG. 3, in a preferred embodiment of the invention, themodular miniature unmanned aircraft with vectored thrust controlcomprises eight major components: the airframe 102, two fins 108, twocombination dihedral braces/landing skids 110, an electronics module104, and thrust vectoring (T/V) modules 106. Preferably, the airframe,fins, and skids are low cost disposable elements of the system.Referring also to FIG. 4, the electronics module 104 houses the vehiclesavionics, propulsion battery, and sensor payload. The T/V modules 106provide propulsive power and control forces. In a preferred embodimentof the invention, the electronics module 104 and T/V modules 106 containall of the necessary equipment to power and control the air vehicle. Assuch, each of these three components can be easily removed and installedon a replacement or mission-specific airframe.

Referring to FIGS. 5 a and 5 b, the thrust vectoring modules 106 combinethe vectoring servo 106 b and electric motor 106 a, shown in the leftside of FIG. 5 b, which are attached to the aircraft 100 by anintegrated breakaway mount. In a preferred embodiment of the invention,magnets 116 are used to attach the T/V modules to the airframe.Anti-rotation brackets 118, shown in the right side of FIG. 5 a arepreferably used to resist thrust and torque loads, yet allow for the T/Vmodules to break free in the event of a ground impact.

Referring to FIGS. 6 a, 6 b, 6 c, and 6 d in a preferred embodiment ofthe invention, lateral and longitudinal control is achieved solelythrough the use of the T/V modules 106. As illustrated in FIGS 6 a and 6b, the T/V modules 106 move in unison for pitch control; and, asillustrated in FIGS. 6 c and 6 d, the T/V modules move differentiallyfor roll control. Yaw control is achieved through differential thrustcommands to the T/V modules.

Referring to FIGS. 7 a, 7 b, 7 c, and 7 d, because the airframe 102 doesnot require control surfaces or other integrated systems, the airframecan be folded to significantly reduce the packed size of the airvehicle. The folding scheme includes four integrated hinges A, B, C, andD, as illustrated in FIG. 7 b. Two dihedral hinges A and a chord-wisehinge B are located on the upper surface of the aircraft, and acenterline hinge C is located on the lower surface. When deflected, thetip dihedral hinge locks the chord-wise hinge, thereby minimizing theamount of hardware needed to rigidize the airframe, as in FIGS. 7 c and7 d.

Referring to FIGS. 8 a, 8 b, 8 c, and 8 d, the landing skids 110, alsoreferred to as dihedral braces, respectively lock the dihedral hinges A,and the centerline avionics/payload pod 104 locks the centerline hingeC. These are the only fasteners needed to hold the airframe in thedeployed configuration.

Referring to FIG. 9, a flowchart 900 illustrates a method forcontrolling a flight path of an unmanned aerial vehicle (UAV), such as amodular miniature unmanned aircraft with vectored thrust control,according to a preferred embodiment of the invention. In the first step905, instructions for controlling the speed and direction of the modularminiature unmanned aircraft are transmitted by a user to the electronicsmodule. In the second step 910, the electronics module converts theseinstructions into commands which are sent to the two thrust vectoringmodules. Finally, in the third step 915, the T/V modules provide thrustin the appropriate directions and magnitudes to cause the modularminiature unmanned aircraft to change direction, thereby controlling theflight path of the modular miniature unmanned aircraft both laterallyand longitudinally.

While the foregoing detailed description has described particularpreferred embodiments of this invention, it is to be understood that theabove description is illustrative only and not limiting of the disclosedinvention. While preferred embodiments of the present invention havebeen shown and described herein, it will be obvious to those skilled inthe art that such embodiments are provided by way of example only.Numerous variations, changes, and substitutions will now occur to thoseskilled in the art without departing from the invention.

What is claimed is:
 1. An aircraft for unmanned aviation, comprising: anairframe having a fixed wing attached thereto; a plurality of finsattached to a rear portion of the airframe; at least a first thrustvectoring module and a second thrust vectoring module, the at least twothrust vectoring modules being configured to (i) provide lateral andlongitudinal control to the aircraft by directly controlling a thrustvector, and (ii) to independently control pitch, roll, and yaw of theaircraft, each of the at least two thrust vectoring modules is attachedto the fixed wing by an integrated non-destructive breakaway mount, eachthrust vectoring module being independently articulable with respect toa portion of the fixed wing to which it is attached; and an electronicsmodule configured to provide commands to the at least two thrustvectoring modules, wherein the breakaway mount is capable of breakingaway upon impact.
 2. The aircraft of claim 1, wherein each of the atleast two thrust vectoring modules comprises a directly articulatedelectrical motor.
 3. The aircraft of claim 1, wherein the airframe isdisposable and foldable into a compact, stowable configuration.
 4. Theaircraft of claim 1, wherein the aircraft is configured for executing aturn having a radius of less than or equal to one wing span over a rangeof airspeeds from zero to a maximum speed of the aircraft.
 5. Theaircraft of claim 4, wherein the aircraft is further configured forexecuting a turn having a radius of less than or equal to one wing spanwhile in a post-stall condition.
 6. The aircraft of claim 1, wherein theairframe comprises a mission-specific airframe.
 7. The aircraft of claim6, wherein the airframe further comprises a mission-specific airframebased on an atmospheric condition or a weather condition.
 8. Theaircraft of claim 1, wherein the non-destructive breakaway mountcomprises a magnetic mount.
 9. A control system for controlling a flightpath of an unmanned aerial vehicle having an airframe with a fixed wingattached thereto, the system comprising: at least a first thrustvectoring module and a second thrust vectoring module, the at least twothrust vectoring modules being configured to (i) provide lateral andlongitudinal control to the vehicle by directly controlling a thrustvector, and (ii) to independently control pitch, roll, and yaw of theaircraft, each of the at least two thrust vectoring modules is attachedto the fixed wing by an integrated non-destructive breakaway mount, eachthrust vectoring module being independently articulable with respect toa portion of the fixed wing to which it is attached; and an electronicsmodule configured to provide commands to the at least two thrustvectoring modules based on instructions received from a user of thecontrol system, wherein the breakaway mount is capable of breaking awayupon impact.
 10. The control system of claim 9, wherein each of the atleast two thrust vectoring modules comprises a directly articulatedelectrical motor.
 11. The control system of claim 9, wherein the controlsystem is configured for enabling the vehicle to execute a turn having aradius of less than or equal to one wing span over a range of airspeedsfrom zero to a maximum speed of the vehicle.
 12. The control system ofclaim 11, wherein the control system is further configured for enablingthe vehicle to execute a turn having a radius of less than or equal toone wing span while in a post-stall condition.
 13. The control system ofclaim 9, wherein the non-destructive breakaway mount comprises amagnetic mount.
 14. A method for controlling an unmanned aerial vehiclehaving an airframe with a fixed wing attached thereto, the methodcomprising the steps of: transmitting a control signal to an electronicsmodule, the control signal including instructions for controlling aspeed and a direction of the vehicle; causing the electronics module toprovide a command to each of at least a first thrust vectoring moduleand a second thrust vectoring module; causing each of the at least firstthrust vectoring module and second thrust vectoring module to providethrust such that the vehicle is laterally and longitudinally controlled,each thrust vectoring module being independently articulable withrespect to a portion of the fixed wing to which it is attached; andusing non-destructive breakaway mounts to cause the first and secondthrust vectoring modules to break away from the fixed wing upon impact.15. The method of claim 14, wherein the step of causing each of the atleast first and second thrust vectoring modules to provide thrustfurther includes causing each of the at least first and second thrustvectoring modules to independently control a pitch, a roll, and a yaw ofthe vehicle.
 16. The method of claim 14, wherein each of the at leasttwo thrust vectoring modules comprises a directly articulated electricalmotor.
 17. The method of claim 14, wherein the step of causing each ofthe at least first thrust vectoring module and second thrust vectoringmodule to provide thrust such that the vehicle is laterally andlongitudinally controlled further comprises enabling the vehicle toexecute a turn having a radius of less than or equal to one wing spanover a range of airspeeds from zero to a maximum speed of the vehicle.18. The method of claim 17, wherein the step of enabling the vehicle toexecute tight-radius high-speed turns over a wide range of airspeedsfurther comprises enabling the vehicle to execute a turn having a radiusof less than or equal to one wing span while in a post-stall condition.19. The method of claim 14, wherein the non-destructive breakaway mountcomprises a magnetic mount.